WO1997019773A1

WO1997019773A1 - Mould-pressing machine with liquid-mist injection

Info

Publication number: WO1997019773A1
Application number: PCT/DK1996/000471
Authority: WO
Inventors: Ole Oksby Hansen
Original assignee: Georg Fischer Disa AS
Current assignee: Georg Fischer Disa AS
Priority date: 1995-11-30
Filing date: 1996-11-15
Publication date: 1997-06-05
Anticipated expiration: 1998-05-30
Also published as: US5881797A; DK135395A; JPH10511316A; ES2134020T3; ATE180188T1; DK171731B1; DE69602542T2; EP0866737A1; JP2998904B2; AU1029797A; EP0866737B1; DE69602542D1

Abstract

In a mould-pressing machine (not shown) with liquid-mist injection, in which are used atomizing nozzles (of which one is shown) with a vortex chamber (27) delivering atomized liquid mixed with air through outlet apertures (28), the atomizing air nozzle or nozzles (21a) being constantly supplied with compressed air through a pressure conduit (29) while the liquid nozzle (21) solely receives liquid under pressure through a liquid channel (30) and a slave valve (31, 32, 33) controlled by the liquid pressure in the periods, during which injection of liquid mist is desired, the main new features are that a vortex chamber (24) is provided upstream of the vortex chamber (27), and that between these two vortex chambers a flow path (25, 25a, 26) is provided to interconnect the two vortex chambers (24, 27), through which flow path the liquid mist having been formed in the vortex chamber (24) is forced to pass and change its direction and velocity of flow at least once, thus reducing the droplet size of the liquid mist. With this arrangement, it is possible to form a liquid mist having smaller and more uniform droplets and to reduce the consumption and waste of liquid, at the same time as a good lubrication of the mould walls is ensured.

Description

MOULD-PRESSING MACHINE WITH LIQUID-MIST INJECTION

TECHNICAL FIELD

The present invention relates to a mould-pressing machine with liquid-mist injection via at least one spray nozzle and of the kind set forth in the preamble of claim 1.

BACKGROUND ART

Mould-pressing machines of the kind referred to above are e.g. known from DE-A1-4,442, 846 and US-A-4 ,791, 974.

In mould-pressing machines of the kind referred to above, usually being adapted to operate automatically producing series of casting moulds or casting-mould parts, it is of crucial importance that the correct quantity of liquid mist be injected in each cycle. Thus, an excess of liquid mist will, in addition to increasing the costs, create an unnecessary load on the environment, while too small quantities of liquid mist will result in an insufficient "lubrication" of the mould-chamber walls, in the worst case possibly causing parts of the compacted object to stick to the patterns mounted on the mould-chamber walls and thus make the mould part unsuitable for pouring.

Thus, it is desirable to inject the least possible quan- tity of liquid with the liquid mist, while at the same time ensuring with absolute certainty that the mould is lubricated sufficiently.

It is a relatively simple matter to ensure that the quan- tity being supplied to the system in each operating cycle is held below a predetermined upper limit, this effect e.g. being attainable by means of a suitably time-con¬ trolled and cycle-controlled pump only applying pressure to the liquid to be atomized in a period corresponding to the desired quantity of liquid mist for each operating cycle. Thus, the maximum quantity of liquid that it is possible to advance through the liquid path with a given pressure at a given moment in time sets the upper limit for the quantity of liquid.

On the other hand it can, however, be difficult to set the lower limit for the quantity of liquid being supplied to the liquid mist, a number of relationships coming into play. Thus, it is of primary importance that the liquid quantity being supplied is converted into a uniform liquid mist being distributed uniformly on the mould chamber walls, so that a sufficient quantity of liquid will be deposited on these walls to provide the requisite lubrication. If the nozzle aperture or other parts of the nozzle are contaminated by particulate mould material or other particles, this will have a negative effect on the formation of the liquid mist and the quantity of liquid being introduced into the mould chamber.

For this reason, the prior art referred to initially comprises the use of nozzles, in which it is possible to maintain a continuous air stream through the outlet aper¬ ture, making it difficult for particles from the mould chamber to penetrate into the apertures.

In these nozzles, the liquid mist is formed by liquid being injected from a first nozzle aperture into a vortex chamber, in which it is mixed with the atomizing air being blown into the vortex chamber from a second nozzle aperture, after which the liquid mist is discharged from the outlet aperture or apertures.

With this known technology, it has been difficult to form a liquid mist with fine and uniform droplets. In the prior art this makes it necessary to supply more liquid to the liquid mist than would have been necessary, if the liquid mist were more uniform and had finer drop- lets.

Further, it has been necessary to use relatively complex valves for shutting-off the liquid at the first nozzle aperture, because this valve is of substantial importance for the accuracy and precision with which the liquid can be delivered to the vortex chamber. It has, however, frequently been necessary to supply a greater quantity of liquid in order to compensate for inaccuracies and lack of precision in the delivery of the liquid. In addi- tion to this, the possibility of liquid leaks occurring, e.g. due to particles - in spite of the continuous stream of air - having penetrated from the mould chamber and in through the outlet aperture to the shut-off valve at the nozzle aperture, has made it necessary to construct the valve in a complicated manner in order to safeguard the operation, and to supply a greater amount of liquid in order to compensate for possible leaks, respectively.

DISCLOSURE OF THE INVENTION

On this background, it iε the object of the present in¬ vention to indicate the construction of a mould-pressing machine of the kind referred to initially, with which it is possible not only to set an upper limit for the amount of liquid mist being injected into the mould chamber during each cycle, but also to set a reliable lower limit for this amount and reduce the quantity of liquid that it is necessary to supply to the liquid mist in each operating cycle, and this object is achieved by means of the features set forth in the characterizing clause of claim 1. With this arrangement, the liquid mist will be formed with finer droplets, and it will be more difficult for particles to penetrate from the outlet aperture or apertures in the upstream direction to the first nozzle aperture, the latter advantage again making it possible to relax the demands on the shut-off valve and its con¬ struction, and it will not be necessary to use the full atomization air pressure during the periods in which spray mist is not being formed in order to protect the first nozzle aperture against intruding particles.

Even though the first and the second vortex chamber as well as the flow path referred to may in so far be shaped in any manner, it is preferred according to the invention to have these parts constructed in the manner set forth in claim 2.

The arrangement set forth in claim 3 makes it possible in a simple manner to manufacture, dismantle and clean the nozzle with the two vortex chambers, as well as to alter the nozzle characteristics by exchanging the body referred to with another.

By constructing the nozzle with its associated shut-off valve in the manner set forth in claim 4, it is possible to achieve a simple construction of the valve with low inertia and friction. Claim 5 relates to a preferred embodiment according to the invention having a shut-off valve being constructed in an extremely simple manner and being robust.

The embodiment of the invention set forth in claim 4 makes it still simpler to manufacture, dismantle and clean the nozzle.

With the embodiment of the machine according to the in¬ vention set forth in claim 7 it is possible in a simple manner to make the liquid pressure proportional to the pressure of the atomizing air.

If the machine is additionally constructed in the manner set forth in claim 8, it is possible in a simple manner to achieve an intermittently varying pressure for the atomizing air, co-ordinated in time with the pressure in the liquid being supplied to the first nozzle aperture, and also to vary the pressures of the liquid and the air using the same adjustment means.

With the arrangement of the machine set forth in claim 9 it is possible to achieve a time delay in the generation of pressure at the controlled pump and hence in the li¬ quid-conducting conduit, and the delivery of the liquid from the first nozzle aperture to the first vortex cham¬ ber, it being possible to adapt said delay to compensate for the delay arising in the atomizing-air conduit and at the delivery of the atomizing air from the second nozzle aperture.

Altogether, the construction of the machine according to the invention, including i.a. the use of two vortex chambers in the spray nozzles, makes it possible to pro¬ vide a machine of simpler construction and capable of in a safe and reliable manner producing a liquid mist with fine and homogeneous droplets whilst consuming less liquid than the previously known equipment. The use of two vortex chambers in each spray nozzle contrasts with the usual design philosophy in this field, because the normal prac¬ tice is to construct the nozzles in the simplest possible manner to make replacements less costly and simplify the cleaning.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed part of the present description, the invention will be explained in more detail with refer¬ ence to the exemplary embodiments of the relevant parts of a mould-pressing machine according to the invention shown in the drawings, in which Figure l is an overall view showing only those parts of the mould-pressing machine according to the invention with associated equipment necessary for the understanding of the invention, Figure 2 is a longitudinal sectional view of a nozzle used in the machine according to the invention,

Figure 3 at an enlarged scale shows the forwardmost part of the nozzle shown in Figure 2, showing the nozzle head and the valve according to the invention, and Figure 4 diagrammatically shows an exemplary embodiment of a system of components, according to the invention advantageously being used for controlling and regulating the supply and pressure of liquid and air for the nozzles. DESCRIPTION OF THE PREFERRED EMBODIMENT

The drawing shows solely those parts of a mould-pressing machine with associated auxiliary equipment necessary for the understanding of the invention. As persons skilled in this art will know, a mould-pressing machine of the kind here referred to requires for its operation various further means and mechanisms, the construction of which and co-operation of which with the components shown will be known to these persons.

Thus, Figure 1 shows a mould chamber 1 bounded by four walls 2-5 visible in Figure 1, as well as by two further walls (not shown) situated in front of and behind the plane of the drawing, respectively. At least one of these walls, constituting the pattern-carrying wall or one of such walls, is adapted to be moved relative to the remain¬ ing walls in such a manner, that particulate material, e.g. mould sand, may be compacted in the mould chamber 1 by the pattern carrier or carriers, so as in a manner known per se to form a casting-mould part corresponding to the pattern impression.

To prevent the mould sand from adhering to the patterns mounted on the two walls mentioned but not shown, a suit¬ able liquid mixed with air is injected through a number of, in the example shown four, nozzles 6-9 of mutually identical construction.

In the example shown, compressed air is constantly being supplied to the nozzles 6-9 from a compressed-air source 10 through a branched compressed-air conduit 11. The liquid is supplied from the liquid space 14 in a liquid reservoir 13 through a time-controlled pump 15 and a branched liquid conduit 12 to the nozzles 6-9.

The mode of operation of the nozzles 6, being - of course - identical to the mode of operation of the remaining nozzles 7-9, is explained below with reference to Figures 2 and 3.

The air is supplied via the connector lie to the air channel 29 formed between the outer tube 22 and the inner tube 23. The liquid is supplied via the liquid connector 12a into the liquid channel 30 constituted by a central bore in the inner tube 23. The liquid channel 30 leads to the valve means 31-33. In the example shown, this valve means is formed by the valve seat 32 constituted by an elastic O-ring, against which the valve body in the form of a ball 31 lies in abutment biased by a spring 33. This valve means constitutes a non-return valve en¬ suring that the liquid can only flow forward to the li¬ quid-nozzle aperture 21 constituting the first nozzle aperture, from which the liquid cannot flow back into the liquid channel 30 because of the valve means. If a sufficiently high pressure is applied to the liquid in the liquid channel 30 to overcome the elastic force acting upon the valve member 31 by the spring 33, liquid will flow from the liquid channel 30 in through the valve seat 32 past the valve member 31 and continue in the forward direction through the liquid-nozzle housing 36 through bores 38,39 to the liquid nozzle 21, from where it is ejected into the first vortex chamber 24.

The first bore 38, being open outwardly at the end facing the valve member 31, constitutes both a liquid channel and a spring housing for the spring 33, and the ledge at the transition from the bore 38 to the bore 39, the latter having a smaller diameter than the former, constitutes the seat for the spring 33. The liquid-nozzle housing 36 is preferably made in one piece and secured to the inner tube 23 by means of a threaded connection or other secur- ing means, and the connection between the liquid-nozzle housing 36 and the inner tube 23 may be sealed with an O-ring 37. As will be evident from the drawing, the li¬ quid-nozzle housing 36 can be manufactured in a simple manner, e.g. by means of axial boring and other machining operations. It is also evident from the drawing that when the liquid-nozzle housing 36 is removed from the inner tube 23, the valve components 31 and 33 are im¬ mediately accessible for removal, and the O-ring 37 can be extracted making it easy to clean all these components.

The air channel 29, in the example shown extending coaxi¬ ally about the liquid-nozzle housing 36, debouches in an air-nozzle aperture 21a constituting the second nozzle aperture and being situated coaxially about the liquid- -nozzle aperture 21.

When pressure is applied to the liquid and the air, they will flow out through the first and the second nozzle aperture 21 and 21a, respectively, and be intermixed in the first vortex chamber 24 so as to form a liquid mist. At the end of the first vortex chamber 24, formed in the vortex-chamber body 20, the liquid mist flows radially outwardly through holes 25a formed in the body 20 to the annular chamber 25. From the annular chamber 25, the liquid mist flows in the forward direction through a gap 26 or grooves 26, formed in a peripheral surface on the body 20 at the end facing away from the entrance opening to the first vortex chamber 24, and from the gap or the grooves 26, the liquid mist flows into the second vortex chamber 27 .

As mentioned above, the connection between the annular chamber 25 and the second vortex chamber 27 may be con- stituted by either a coaxial gap 26 or grooves 26. If grooves 26 are used, they can extend in a more or less helical manner, so as to produce cyclone-like vortices in the second vortex chamber 27.

From the second vortex chamber 27, the liquid mist flows in the forward direction to the exit aperture 28, in the example shown being formed by fine holes 28 situated symmetrically about a nozzle axis 40, and the holes 28 extend at a skew angle so as to substantially lie in a surface of a cone about the axis 40. From the holes 28, the liquid mist is sprayed out into the mould chamber 1.

When the liquid from the liquid nozzle 21 is ejected into the first vortex chamber 24 and is mixed with the atomizing air from the air nozzle 21a, a liquid mist is formed having substantially the same droplet size and uniformity as are formed with the previously known nozzles of this kind. After this, the liquid mist undergoes an additional atomization by passing through the flow path formed by the radial holes 25a, the annular chamber 25 and the gap or grooves 26, ending at the internal end wall of the second vortex chamber 27. By passing through this flow path past obstructions producing velocity and pressure variations, wall friction, turbulence and col- lisions of heavier droplets with the walls, the droplet size of the mist is reduced and made more uniform than can be achieved with one single vortex chamber.

In normal operation, air flows continuously through the air channel 29 and through the vortex chambers 24, 27 via the flow path 25, 25a, 26 and out through the fine holes 28, thus ensuring that the nozzle will not be clogged by particles from the mould chamber 1. Should, however, a large pressure rise occur in the mould chamber 1, such as may happen when filling mould material into the mould chamber 1, particles can penetrate inwardly through the holes 28 and into the second vortex chamber 27. It will, however, be difficult for the particles to penetrate from the second vortex chamber 27 into the first vortex chamber 24, because the flow path 25, 25a, 26 constitutes an obstacle more difficult for the heavier particles than the air to pass, and due to their weight, these heavier particles will hit the walls and be retarded each time the flow path changes direction, thus preventing particles from being shot into the first vortex chamber with a high velocity. Substantially at the same time, a pressure wave will travel through the air channel 29, thus reducing the risk for the liquid-nozzle aperture 21 of being contaminated with particles from outside. One of the effects of this is that the shut-off valve for the liquid-nozzle aperture 21 need not be constructed in a particularly contamination-resistant manner, for which reason it can be constructed in the simple manner of a non-return valve as referred to above. This arrangement makes it possible to construct the liquid path in the forward direction to the valve 31-33 in any desirable manner, and makes it possible to construct the valve body with a low inertia and friction, complex connecting devices, increasing the weight and the possibility of friction, not being necessary. Further, the non-return valve 31-33 delimits the volume, from which liquid can leak during the intervals in which spray mist is not to be formed, substantially to the volume constituted by the bores 38, 39 in the liquid-nozzle housing 36, thus reducing the loss of liquid.

Since the risk and the possibility of particles from the mould chamber 1 penetrating into the innermost parts of the nozzle 6 are reduced, it is also possible to lower the pressure in the air channel 29 in the periods in which spray mist is not to be formed, because the air pressure only periodically needs to be sufficiently high to be able to blow the exit apertures 28 clean.

In order to simplify manufacture and cleaning, the vortex- -cha ber body 20 can be made in one piece to be inserted in the nozzle-outlet housing 35, likewise being made in one piece. Further, the nozzle-outlet housing 35 can be removably secured to the outer tube 22 of the nozzle 6, e.g. by means of a threaded connection or the like, the connection between the nozzle-outlet housing 35 and the outer tube 22 being sealed with a seal 34, preferably in the form of a flexible O-ring.

If likewise, the outer tube 22 and inner tube 23 are removably mounted, e.g. by means of a threaded connection, in a nozzle-mounting housing 41, it is possible to dis- mantle the nozzle 6 into its individual components, making it possible in a simple manner to clean, exchange and alter these components.

Since the machine according to the invention does not require a continuous supply of air under pressure to the spray nozzles 6-9, the machine can advantageously be constructed with an intermittent supply of air under pressure to the nozzles 6-9, this e.g. being achieved by constructing the parts of the machine in the manner shown in Figure 4 .

In Figure 4, compressed air is received from a compressed -air source to the compressed-air conduit Ila. The com- pressed-air conduit Ila is connected to a compressed-air branch conduit lib, the latter leading via a reducing valve 18a and a controlled valve 18, preferably a solenoid valve, to a branching point, at which the compressed-air conduit forms two branches, viz. a compressed-air conduit lie and a compressed-air conduit lid.

The compressed-air conduit lid leads via the non-return valve 19 to the compressed-air conduit 11 supplying com¬ pressed air to the nozzles 6-9. Further, the compressed- -air conduit 11 is connected to the compressed-air supply conduit Ila through a restricted orifice 17, so that when compressed air is supplied to the compressed-air supply conduit Ila, it is also ensured via the restricted orifice 17 that compressed air is supplied to the com- pressed-air conduit 11 and the nozzles 6-9.

The compressed-air branch conduit lie leads to a pump 15 via a restricted orifice 16, said pump 15 being con¬ trolled and possibly actuated by compressed air. This pump builds up the liquid pressure in the liquid conduit 12 leading to the spray nozzles 6-9 by pumping liquid from a liquid space 14 in a liquid reservoir 13 to a liquid conduit 12. The flow path between the pump 15 and the liquid conduit 12 may comprise a pressure-controlled switching valve 15a, reacting on the presence of a higher pressure in the liquid conduit 12 to the spray nozzles 6-9 than the pressure from the pump in the conduit 12c by shutting off the latter and switching the liquid con¬ duit 12 from the conduit 12c to a liquid conduit 12b returning liquid to the liquid reservoir 13 and the let¬ ter's upper part comprising an air space 14a above the liquid space 14.

The pressure-controlling parts of the machinery shown in Figure 4 function in the following manner. The starting point is the part of the machine cycle, in which liquid mist is not to be formed, the solenoid valve 18 for this reason being closed. A compressed-air source 10 shown in Figure 1 supplies compressed air to the compressed-air supply conduit Ila. From the latter, the compressed air is supplied via the restricted orifice 17 at a reduced pressure to the compressed-air conduit 11, from which the compressed air is supplied to the spray nozzles 6-9 so as to provide a continuous flow of compressed air through the nozzles and into the mould chamber 1 shown in Figure 1.

When the machine operating cycle approaches the moment in time, at which a spray mist is to be formed, the sole¬ noid valve 18 opens immediately before this mist is to be formed. This causes a pressure, previously having been adjusted on the reducing valve 18a, to propagate in the forward direction to the branch conduit lie, lid. The compressed air with the pre-adjusted pressure is conducted by the compressed-air conduit lid via the non- -return valve 19 to the compressed-air conduit 11, the pressure in the latter being built up toward a value determined by the setting of the reducing valve 18a, and this pressure build-up propagates to the spray nozzles 6-9, thus causing the flow-through of air in these to be built up to a desired value.

At the same time as a build-up of the pressure in the compressed-air conduit 11 takes place, a build-up of air pressure takes place in the compressed-air-controlled pump 15 via the restricted orifice or throttling device 16. The throttling device 16 produces a delay of the build-up of air pressure at the compressed-air-controlled pump 15, and this delay is harmonized with the delay taking place in the build-up of air pressure to the spray nozzles 6-9. When the pressure at the compressed-air- control pump 15 reaches a switching-threshold value, the pump 15 starts and builds up a pressure in the liquid conduit 12c, 12, during which the liquid conduit 12c is possibly connected to the liquid conduit 12 by a switching valve 15a, if the connection between the liquid 12c and the liquid conduit 12 has been interrupted. This liquid pressure propagates so to speak without delay through the liquid conduit to the spray nozzles 6-9, the latter then producing a liquid mist as described previously and being sprayed in the mould chamber.

During this course of events, the solenoid valve 18 is subjected to a control, e.g. a time control or a control on the basis of measurement of the liquid flow in the liquid conduit producing a signal for closing the solenoid valve 18. When the solenoid valve 18 is closed, the pres- sure in the compressed-air conduits lie and lid, that are relatively short, falls relatively quickly, causing the non-return valve 19 to close and the pump 15 to stop. In this manner, the liquid flow to the spray nozzles 6-9 ceases without substantial time delay, whereas the air pressure in the air conduit 11 falls gradually to its previous value as the air is being discharged via the spray nozzles 6-9.

By arranging the pressure control in the manner referred to above it is possible using simple means to provide control of the quantity of liquid being supplied to the spray nozzles 6-9, and this metering of liquid may be carried out using simple time control or other means. At the same time it is possible to adjust both the pressure of the atomizing air and the pressure in the liquid for forming the liquid mist by a single setting of the re¬ ducing valve 18a. Further, when the pressure in the com¬ pressed air supplied to the spray nozzles 6-9 varies intermittently, it is permissible to use pressures for the formation of liquid mist producing such outlet pres¬ sures and velocities from the spray nozzles 6-9 that could cause damage to the moulds being formed in the mould chamber in the regions of the outlet apertures of the spray nozzles 6-9, because prior to the formation of a new mould, this pressure is lowered to a level at which damage cannot be caused to the newly introduced mould material or the finished mould being present in the mould chamber.

A more detailed description of the equipment (not shown) , that the mould-pressing machine according to the invention must comprise or be associated with, such as filling means for filling particulate material in the mould cham- ber and pressing-force means to move at least one ould- -chamber wall towards at least one other such in order to compress the particulate material and to eject the finished mould, may be found in DE patent application No. 4,442,846-Al and US patent publication No. 4,791,974, and the spray nozzles and the liquid-return arrangement may be constructed in the manner described in DK patent application No. 1351/93, the content of these documents to be considered part of the present description to the extent to which they comprise such a description. LIST OF PARTS

1 mould chamber

2 wall 3 wall

4 wall

5 wall

6 spray nozzle

7 spray nozzle 8 spray nozzle

9 spray nozzle

10 compressed-air source

11 compressed-air conduit

Ila compressed-air supply conduit lib compressed-air branch conduit lie compressed-air branch conduit lid compressed-air branch conduit lie connector

12 liquid conduit 12a liquid connector

12b liquid conduit

12c liquid conduit

13 liquid reservoir

14 liquid space 14a air space

15 time-controlled pump

15a pressure-controlled switching valve 15b

16 restricted orifice / throttling device 17 restricted orifice

18 controlled valve/solenoid valve 18a reducing valve

19 non-return valve 0 vortex-chamber body 21 liquid-nozzle aperture

21a liquid-air-nozzle aperture

22 outer tube

23 inner tube

24 first vortex chamber

25 annular chamber

25a holes

26 gap/grooves

27 second vortex chamber

28 exit aperture/fine holes

29 air channel

30 liquid channel

31 valve member/ball )

32 valve seat ) ^valve

33 spring ) ^means

34 seal

35 nozzle-outlet housing

36 liquid-nozzle housing

37 O-ring

38 first bore

39 bore

40 nozzle axis

41 nozzle-mounting housing

Claims

C L A I M S :

1. Mould-pressing machine with liquid-mist injection via at least one spray nozzle for producing casting moulds or casting-mould parts by compacting particulate material, especially mould sand, and of the kind comprising a) a mould chamber (1) bounded by at least one mould- -chamber wall (2-5) , b) filling means for filling particulate material into the mould chamber (1) , c) pressing-force means adapted to move at least one mould-chamber wall, possibly carrying at least one pattern mounted thereon, towards at least one other mould-chamber wall so as to compact the particulate material being thereinbetween, as well as d) liquid-applying means adapted to introduce a liquid mist in the mould chamber (1) prior to the latter being filled with particulate material by means of said filling means, said liquid mist being formed by means of at leaεt one atomizing nozzle (6-9) , in which the liquid supplied under pressure is atomized by means of an air current, each atomizing nozzle (6-9) comprising dl) a vortex chamber (27) comprising at least one outlet aperture (28) for a liquid-in-air dispersal and, positioned upstream of said aperture (28) , d2) at least one first nozzle aperture (21) adapted for the supply of the liquid, and d3) at least one second nozzle aperture (21a) situated in the immediate vicinity of said first nozzle aper¬ ture (21) and adapted for the supply of atomizing air, as well as d4) a valve (31-33) adapted to shut off said first nozzle aperture (21) and having a valve member (31) spring- -biased towards the closed position and capable of being moved away from said closed position under the influence of the pressure in the liquid conduit (12) leading to said first nozzle aperture (21) , e) air supply means (10,11) for supplying atomizing air under pressure to said second nozzle aperture or apertures (21a) , as well as f) pressure-creating means (15) for applying pressure to the conduit (12) leading to the first nozzle aperture or apertures (21) solely during the periods during which production of liquid is desired, c h a r a c t e r i z e d by g) a first vortex chamber (24) downstream of said first and second nozzle aperture or apertures (21,21a) and upstream of the vortex chamber (27) mentioned

(in item dl) above comprising the at least one outlet aperture (28) and constituting a second vortex cham¬ ber (27) , the connection between said first (24) and said second (27) vortex chambers being consti- tuted by a flow path (25,25a,26) with a reduced flow cross-sectional area and being so shaped as to produce at least one change in the direction of flow in the flow between the two vortex chambers (24,27) .

2. Machine according to claim 1, c h a r a c t e r¬ i z e d in a) that said first vortex chamber (24) extends substan¬ tially coaxially with said first nozzle aperture (21), b) that the flow path (25, 25a, 26) from said first vortex chamber (24) is constituted by substantially radial holes (25a) debouching in an annular chamber (25) , and c) that from said annular chamber (25) , said flow path continues via a gap (26) or a number of grooves situated in a substantially axial peripheral surface and debouching in said second vortex chamber (27) .

3. Machine according to claim 1 or 2 , c h a r a c¬ t e r i z e d in that said first vortex chamber (24) is formed in a body (20) as a substantially axial bore (24) being open at one end and adjacent to its opposite end having substantially radially emerging bores (25a) , said bores (25a) debouching in a circumferential groove (25) , said body (20) having an outer diameter in magnitude within an interval limited by the bottom diameter and the largest edge diameter of said circumferential groove, or peripheral grooves (26) extending from said circum¬ ferential groove (25) and away from the end, at which said bore (24) has itε entrance opening.

4. Machine according to any one or any of the claims 1-3, c h a r a c t e r i z e d in that said valve means

(30,31,32) for shutting off said first nozzle aperture (21) is arranged in the vicinity of the latter in the form of a non-return valve (30,32) .

5. Machine according to claim 4, c h a r a c t e r¬ i z e d in that said non-return valve (30,31,32) com¬ prises a) a valve seat (32) situated close to and upstream of said first nozzle aperture (21) , said valve seat preferably being in the form of an elastic O-ring (32) through which a liquid channel passes on its way to said first nozzle aperture (21) , and b) a preferably spherical valve member (31) situated between said first nozzle aperture (21) and said valve seat (32) and being biased towards the latter, preferably by means of a spring element (33) placed between the valve member (31) and said nozzle aper¬ ture (21) .

6. Machine according to claim 4 or 5, c h a r a c¬ t e r i z e d in that said first liquid-nozzle aperture (21) is provided in a liquid-nozzle housing (36) being made in one piece and forming a removable closure for said liquid channel (30) , said non-return valve means (31,33) being retained between said liquid-nozzle housing (36) and said valve seat (32).

7. Machine according to any one or any of the claims 1-6 and of the kind comprising a compressed-air-controlled pump (15) as a means for applying pressure to the conduit leading to said first nozzle aperture (21) or said second nozzle apertures, c h a r a c t e r i z e d by com¬ pressed-air branch means (lib, lie) leading from the means (10, Ila) to supply compressed air to said second nozzle aperture or apertures and via a controlled valve (18) to said compressed-air-controlled pump (15) .

8. Machine according to claim 7, c h a r a c t e r- i z e d in a) that an adjustable reducing valve (18a) iε situated in the pressure conduit (lib) upstream of the con¬ trolled valve (18) , b) that downstream of said controlled valve (18) a branch conduit (lid) is provided from the compressed-

-air conduit (lie) to the pump (15), said branch conduit (lid) via a non-return valve (19) leading to the compressed-air conduit (11) for the nozzles (6-9) , and c) that said compressed-air conduit (11) for the nozzles (6-9) is connected to the means (10, Ila) for supply¬ ing compressed air via a restricted orifice or throt¬ tling device (17) .

9. Machine according to claim 7 or 8, c h a r a c¬ t e r i z e d by a throttling device (16) inserted in the branch conduit (lie) leading to the controlled pump (15) .